The invention relates generally to clamping devices and particularly to a powered clamp having a toggle action with a self-locking feature.
Powered clamps are commonly used in industrial applications for holding work pieces of many sizes and shapes during forming, welding and/or machining operations. Such devices typically include a pneumatically, hydraulically or electrically actuated cylinder which causes one or more arms to move through a desired range of rotational motion. Furthermore, the user may wish to actuate the arms in a contaminated environment having weld splatter, saw chips, coolants, dust, dirt and the like. One such conventional powered clamp is disclosed in U.S. Pat. No. 5,171,001 entitled “Sealed Power Clamp” which issued on Dec. 15, 1992 and is hereby incorporated herein by reference.
Other traditional clamps have arms which typically move or release pressure upon the work piece when the actuating force is reduced or lost. Furthermore, the machining tolerances of the majority of the internal clamp components must be accurately controlled in order to achieve desired component part motions and to achieve satisfactory clamping forces.
Another powered clamp disclosed in U.S. Pat. No. 5,884,903 entitled “Powered Clamp and Engaging Apparatus” issued on Mar. 23, 1999 and is hereby incorporated by reference. This clamp incorporates a variety of components including a slide, a link, a crank and a hub. The components also combine to provide a lost linear motion device to maximize arm unlocking forces. While the above-mentioned clamps have satisfactorily performed a desired function, it is desirable to provide a clamp having a reduced number of components. Also, it is desirable to provide a powered clamp that will not release its grip when actuating pressure is removed.
In accordance with the present invention, an embodiment of the apparatus performs as a clamp with a moveable member or members which perform a clamping function. The clamp includes a pair of moveable members which mechanically butt against each other to maintain, at least temporarily, a locking position of an arm when actuating forces have been decreased or lost.
The powered clamp apparatus of the present invention is highly advantageous over conventional clamps because the present invention includes a tapered self-locking feature for holding a rotated arm in a desired position even after loss of actuating force occurs. Thus, work pieces will not fall from their locked or engaged positions, thereby preventing work piece and equipment damage. Another advantage of the present invention apparatus is that the overall packaging envelope required by the clamp is reduced by aligning the transverse axis of a rotating hub with a longitudinal axis of a piston. The present invention is further advantageous by employing a slide rod including an angled surface which selectively engages a seat on the hub when the actuator is in a fully extended position. The slide rod and hub mating surfaces function to restrict movement of the actuator away from the fully extended position regardless of the presence of actuating fluid pressure. The present invention apparatus includes presence of actuating fluid pressure. The present invention apparatus includes an end cap having a pair of fluid ports. The end cap is rotatable about a longitudinal axis of the clamp to allow the user to easily connect the clamp to a fluid power source. Furthermore, the present invention advantageously includes a position sensor operable to indicate the presence or absence of an actuator at a predetermined location. A position sensor may be configured to accommodate electrical connections at twelve different orientations. The present invention apparatus is fully sealed and permanently lubricated and is therefore suitable for use in even the most contaminated environments. The power clamp apparatus is also very compact and lightweight, and may have its clamping or engaging arm easily preset to any one of a number of positions. The total rotational angle of the arm is also adjustable. Additional advantages and features of the present invention will become apparent from the following description and dependent claims, taking in conjunction with the accompanying drawings.